This invention relates to an electric distribution box such as a fuse box, and more particularly to a bus bar structure of an electric distribution box receiving a bus bar through which electric power, supplied from an alternator (ALT), is supplied to various elements.
A battery mounted on an automobile serves as a power source for supplying necessary electric power for igniting an air/fuel mixture, for lighting lamps, for starting an engine and for other purposes. However, a capacity of electric power that can be stored in the battery is limited, and therefore the battery can not continuously supply the necessary electric power to the automobile. Therefore, during the travel of the automobile, electric power has been supplied to various electrical equipments, using a charging apparatus for converting a propelling force of the automobile into electric power.
During the travel of the automobile, such a charging apparatus supplies electric power to the various electrical equipments, and also charges the battery by its excess electric power so that the battery can supply electric power whenever necessary. This charging apparatus comprises a generator (dynamo generator), a regulator, a battery, and a wire harness. When thus using the generator (dynamo generator), electric power, required during the travel, can be supplied by this generator. At this time, if the amount of this supplied electric power is insufficient, the battery also functions as a power source. In contrast, when the amount of generation of the electric power by the generator is larger than the amount of used electric power, the generator charges the battery by its excess electric power. Namely, the generator serves as the power source during the travel, and also serves to charge the battery.
Such generators (dynamo generators) are classified into a DC generator and an alternator (AC generator). In recent years, traffic congestion in and around cities has been terrible, and in such a condition the speed of running of a car is low, and besides since the car frequently stops, the time of idling of the engine much increases. In addition, various accessories, such as a cooler and a heater, consume a large amount of electric power. When the amount of consumption of electric power thus increases, the conventional DC generator can not meet such power consumption by its output power, so that the battery becomes rather discharged. Therefore, in order to deal with this large electric load, there has recently been used an alternator (ALT) having the function of charging the battery even during the idling of the engine. This alternator (ALT) has a slip ring, and therefore has advantages that a brush has a long lifetime since there occurs no spark, that the strength of a rotor at high speed is high, that rectifying characteristics are good and that the charging can be effected even during the idling.
Therefore, driving electric power for driving various on-vehicle equipments, mounted on the automobile, are supplied from the battery when starting the engine and when the engine is stopped, and also such driving electric power is supplied from the alternator (ALT) during the travel of the automobile (during the driving of the engine). The electric power, supplied from the battery, is generally stable, but the electric power, supplied from the alternator (ALT), varies with a running condition of the automobile. Particularly when a large electric current is abruptly supplied to the various on-vehicle equipments, there is a fear that the on-vehicle equipments, supplied with the electric power, are damaged. Therefore, usually, electric power, supplied from the alternator (ALT), is fed via a bus bar to fusible links (F/L) and fuses which serve as protective circuits for preventing electric power, larger than a predetermined value, from being supplied to the various on-vehicle equipments, and thus the electric power is supplied to the various on-vehicle electronic equipments via these fusible links (F/L) and fuses. The electric power is fed from a power supply terminal (connected to the alternator (ALT)) to the various on-vehicle equipments via the bus bar, and the fusible links (F/L) and fuses are connected to the power supply terminal, and these fusible links (F/L) and fuses are gathered in one place to form one component, and function as an electric distribution box.
In a bus bar structure of one conventional electric distribution box as disclosed in JP-UM-B-7-16313, electric power is supplied from an alternator (ALT) to one end of a bus bar via a fusible link (F/L), and then is supplied to various loads from this bus bar. In another conventional bus bar structure as disclosed in JP-A-6-231670, electric power is supplied from an alternator (ALT) to a generally-central portion of a bus bar via a fusible link (F/L), and then is supplied from this bus bar to various loads via fuses. In a further conventional bus bar structure as disclosed in JP-A-9-283004, there is provided a wall covering a bus bar, and a window is formed in this wall.
In the bus bar structures of these conventional electric distribution boxes, however, the generation of heat by the bus bar is not taken into consideration. Namely, although the electric power (electric current), supplied from the alternator (ALT), is larger than electric power (electric current) required by the various on-vehicle equipments, the bus bar structure is uniform.
The various on-vehicle equipments do not require all of the electric power generated by and supplied from the alternator (ALT). Therefore, the various on-vehicle equipments use a necessary amount of electric power out of the electric power (generated by and supplied from the alternator (ALT)), leaving part of this supplied electric power, and the remainder is used for charging a battery. The bus bar for supplying the necessary electric current to the various on-vehicle equipments is different in size from the bus bar for supplying the excess electric current. Namely, the width of the bus bar for supplying the electric power (electric current) to the battery is larger than the width of the bus bar for supplying the necessary electric current of a larger amount to the various on-vehicle equipments.
However, in the bus bar structures of the conventional electric distribution boxes, the width of the bus bar for supplying the electric power (electric current) to the battery is equal to the width of the bus bar for supplying the necessary electric current to the various on-vehicle equipments, and the bus bar for supplying the electric power (electric current) to the battery is formed in continuous relation to the bus bar for supplying the necessary electric current to the various on-vehicle equipments. Namely, the same current flows through the whole of the bus bar. Therefore, all of the electric power (electric current), generated by and supplied from the alternator (ALT), flows through the whole of the bus bar.
Therefore, in the bus bars of each of the conventional electric distribution boxes, when the electric power (electric current), generated by and supplied from the alternator (ALT), is at a peak, the whole of the bus bar serves as a heat-generating body to generate heat, thus inviting a problem that the generation of heat in the electric distribution box can not be sufficiently suppressed, so that it is difficult to suppress a temperature rise within the electric distribution box.